Oxidizing baths containing perchlorofluorocarboxylates



United States Patent OXIDIZING BATHS CONTAINING PERCHLORO- t FLUOROCA RBOXYLATES William E. Hanford, Short Hills, NJ., assignor, by-mesne r assignments, to. Minnesota-Mining and Manufacturing Company,-St.- Paul,-,Minn., a corporation of Delaware No Drawing. Application September 22, 1955 Serial No. 536,011

This invention relates to the use ofperchlorofiuorocarboxylic acids, or salts thereof, having from about 4 to 20 carbon atoms as surface active agents .in bleaching processes. i

In the paper industry there is great difiiculty involved in bleaching wood pulp to a high permanent brightness without alfecting the strength of the cellulosic material and the paper made therefrom. The bleaching solutions have the undesirable property of attacking cellulose and weakening it through chemical reaction and depolymerization, as determined by viscosity measurements.

In the textile industry a careful control is kept of bleaching conditions in order that a satisfiactory bleach is accomplished with the least amount of deleterious action on the fibers. Most of the textile materials are sensitive to bleaching action, hence a strict control of bath temperature, time of immersion, pH and the concentration of bath constituents is maintained The various fibers each have their own processing peculiarities. In the scouring, desizing and processing of fibers of vegetable origin, there are natural color bodies, waxes, pectins and sizings' which make the fabrics water repellent and thus tend to interfere with bleaching and dyeing.

In bleaching fabrics that are dyed in some portions there is the problem of staining due to crocking or due to dye that has washed out of the goods, hence'it is necessary to use a dye conditioning agent. Goods composed of fibers of cellulose and artificial silks that contain colored portions dyed with naphthol and related dyes are not normally fast to active oxygen bleach solutions. The dye loses itsoriginal shade, brightness and luster and appears dull.

I Photographic bleaching baths are used in multicolored photography for the bleaching of the silver image following color-forming development. In the processing of multicolor reversible film and multicolor negative film,

the silver present in all the layers following development is convertedinto a salt by means of a bleaching bath, and the silver salt thus formed is removed by dissolving it in a solvent for the silver salt e. g., hypo. Certain color photographic emulsions contain an organic solvent for color-couplers, such as a waterinsoluble but water permeablecellulose binder or a high boiling crystalline material, and there is' a tendency for these solvents to occludethe metallic silver following development and-to prevent itsconversion into a silver salt have a single step, two steps or multiple steps, and these general types of bleaching use different bleaching chemicals or combinations of them. Probably the most satisfactory of the known bleaching methods is a multiple step system where the pulp is exposed to the action of chlorine or a hypochlorite in one or more steps, followed by a caustic extraction stage in which some solubles are removed. Finally, there are one or more bleaching stages. The pulp can be in a slurry or in the form of a sheet or a wet web.

In the textile industry bleaching is performed on animal fibers such as wool and silk, on vegetable fibers such as cotton and linen, on artificial fibers such as rayon and nylon, in the form of raw stock or carded, spun, woven, knitted orfelted as a fabric. The practical conditions are a scouring with washing and rinsing, followed by bleaching either in a bath or by other means of con- ;tact. When the bleaching is completed in one or several treatments, the excess liquid is removed by rollers or some other device and the material is Washed and dried. The surface active agents used in this inventioncan be incorporated in the bleaching of wood pulp, cellulose by the customary bleaching bath. The coupler originally present in the emulsion layer and the dye formed from it are dissolved in the organic solvent where the-part1- cles of metallic silverwhich are formed during the development step are enclosed so that they can no longer be aifected by the bleaching bath. Unremoved silver causes a haze, a poor. color rendition and hasja deterioratingllaction upon the layers in which'it is located with thefresult that the picture is obliterated.

In the bleaching of wood pulp, the bleaching systems ethers, cellulose esters and other cellulose derivatives, nylon, rayon and other synthetics, starches, sugars, sponges, walnut shells and other nut shells, shellac and other resins, oils, fats, Waxes, soaps, fatty acids, petroleum derivatives, multicolored photographic films, silk, wool, cotton, linen and the other materials susceptible to bleaching.

In some bleaching processes there is the problem that the bleaching effect is not stable and is subject to retrogression or degradation with lapse of time. It is known that bleaching accomplished by the use of reducing or deoxidizing agents is subject to the defect of being transitory, i.e., upon subsequent exposure to air the material reverts to the original color and the bleaching effect is lost.

As a means of insuring bleaching in an economical and practical manner, control of surface tension by the use of surface active agents has been attempted. The best of these surface active agents include aliphatic alcohol sulfates, aliphatic sulfonates, alkylated aromatic sulfonates, aliphatic ketones and alcohols, phenoxy alcohols, sulfonated-dicarboxylic acids, sulfonated oils, derivatives of pyridine bases, mixtures of phenols and hydrogenated phenols, and various mixtures consisting of organic solvents and wetting agents. Most of the surface active agents have limited use in bleaching operations. It is known that when oxidizing compounds are mixed with organic materials the constituents tend to decompose.

. Heretofore, the use of wetting agents has been limited to dilute solvents to avoid formation of unstable mixtures. Surface active agents suitable for use in bleaching processes must be resistant to oxidation and/or hydrolysis in acidic and basic media. They must not cause excessive decomposition of the active bleach component, and they must be capable of increasing the penetrating, emulsifying or dispersing properties of the solvents. Also, their presence must not affect the important physical characteristics of the-immersed material.

The ordinary surface active agents have not been found satisfactory for use under corrosive conditions. They are subject to decomposition or to alteration in structure. They lose their effectiveness as surface active agents and sometimes lead to undesirable bath properties. They cannot be mixed in concentrated bleach mixtures for storage or shipping purposes because there is a-rapid decomposition of components which can assume dangerous proportions. The surface active agents used in this invention help solve many ofthe aforementioned problems. The perchlorofiuorocarboxylic acids and salts increase the prob ability that surfaces will be uniformly wetted and acted upon by the bleaching solution and the surfaces are more effectively cleansed of contamination and foreign matter that interfere with the bleaching action. In processes using high temperatures the surface active agents .act to reduce spray, splash and mist through the lowering of the urface tension; also, the drag-out losses are reduced thereby conserving both the bath constituents and the surface active agents. Further, there is no loss of surface active agents due to chemical decomposition or reaction, and there are no deleterious effects on the bleaching solution or material immersed therein because of a transformation of the surface active agent compounds.

application Serial No. 452,706, filed August 27, 1954.

These surface active agents also shorten the time necessary for a proper bleach by increasing the wetting and penetrating power of the solution, thereby avoiding long and drastic bleaching. In multiphase bleaching systems, i.e., oils, fats, waxes, and the like, in aqueous mixtures,

the lowering of the surface and/orinterfacial tension increases the bleaching rate markedly. The shorter immersion time helps prevent excessive decomposition or depolymerization of the particular material in the process. Also, the surface active agents permit a broader range of temperature and pH, thereby allowing a Wider choice of the most favorable conditions.

Another important result of the use of perchlorofluorocarboxylic acids and salts thereof as surface active agents in bleaching processes is that smaller amounts of expensive bleach agent, e.g., hydrogen peroxide, are required to obtain a necessary degree of bleaching when the surface active agent is present. Further, these surface active agents can be included in concentrated mixtures which are stored or shipped for use as bleaches, disinfectants, germicides or deodorants and which normally are not safe with some ordinary surface active agents. The mixtures may be dry, or in a solvent to form a liquid, cream or paste.

Other benefits derived from the use of these surface active agents in bleaching processes are dependent on the particular bleaching agents, materials and processes involved. These surface active agents can have a stabiliz ing effect on the active components of the bleaching mixture and this can be of significance where the bleach* ing is accomplished in acid media. Acid bleach is generally unsatisfactory because of deterioration of the bleaching solution and of the product. The surface active agents can make acid bleaching practical by stabilizing the solution and by preserving the product through shorter immersion time.

The perchlorofluorocarboxylic acid surface active agents can be used successfully in combination with most bleaching reagents including sulfur dioxide, sulfurous acid, sulfites, bisulfites, hydrosulfites, chlorine, chlorites, hypo chlorites, peroxides, persulfates, perborates, percarbonates, persilicates, permanganate, ozone, aqua regia, alkali metal ferricyanides, sulfur dioxide, and the like, with or without stabilizing agents such as sodium silicate, caustic soda, soda ash, or the like, or other agents or compounds such as epsom salts, formaldehyde, phenoxy alcohols, catalytic salts, e.g., cobalt and nickel chlorides, sulfates or nitrates, and the like, which give beneficial effects whe incorporated in certain bleaching mixtures.

In hot, highly agitated bleaching baths the amount of frothing can be controlled with the surface active agents and there is less need for a cold water spray.

The perchlorofluorocarboxylic acids which can be used are. prepared in a variety of ways. For example, they may be produced by subjecting perhalogenated aliphatic olefins, having at least 7 carbon atoms and being at least half fluorinated, to oxidation conditions in the presence of a vigorous oxidation reagent, such as free oxygen in the presence of ultraviolet light, free oxygen in the presence of ultraviolet light and elemental chlorine, free oxygen in the presence of elemental fluorine, and permanganate salts in a liquid medium. Preparation of the acids according to this method is disclosed in copending The acids also may be prepared by subjecting ali phatic perhalogenated high pplymers to thermal cracking conditions to produce lower molecular weight materials having molecular weights in the oil or wax range and subjecting these materials to'ox'idation at a temperature not higher than about 10 C. in the presence of a permanganate salt in a liquid medium. lrocesses ofthis type i are disclosed in copending application'Serial No. 452,704,

filed August 27, 1954. l v.

Also, the perchlorofluorocarboxylic acids used in: this invention may be prepared by heating fluorinecontaining telomers, having the general formula,

in which R is a perhalomethyl radical having a total atomic weight not higher than 146.5, X and X are fluorine or chlorine atoms, and n is an integer from 2 to 16, with fuming sulfuric acid at a temperature of at least 125 C. This process produces carboxylic acids having' the formula, A

in which Z is a carboxylic acid radical or a perhalomethyl radical having a total atomic weight not in excess of 146.5 and n is an integer from 2 to 16. The preparation of these acids is disclosed in copending application Serial No. 452,703, filed August 27, 1954, now Patent No. 2,806,865.

The preferred process for the preparation of perchloro fluorocarboxylic acids useful in the process of the present invention is the hydrolysis of telomers produced by telornerizing perhaloolefins using sulfuryl chloride as a telogen. The hydrolyzed telomer has the formula,

in which Z is a carboxy-lic acid radical or a perhalornethyl radical in which all the halogen atoms are fluorine or chlorine and n is an integer from 2 to 16. The preparation of these acids is disclosed in copending application Serial No. 452,705, filed August 27, 1954, now Patent No. 2,806,866.

The perchlorofluorocarboxylic acid salts which may be used in the present invention are those disclosed in copending application Serial No. 501,782, filed April 18, 1955, now Patent No. 2,806,867, the preferred salts having the formula,

Example 1 Carboxyethyl cellulose (1 kg.) is slurried in 87 percent isopropanol and neutralized to a pH of 7 with phosphoric acid. The mixture is heated to 60 C. and treated with, sodium chlorite solution (1 gram of a 25 percent aqueous solution with 6 percent available chlorine) and 0.3 gram of the potassium salt of C1(CF 'CFCl) CF COOH The slurry is agitated for 15 minutes then filtered, Washed with methanol and water, and air dried. Example, 2 I Afi-sh oil (500 grams) is emulsified by the addition of water. I Afterthe addition of 200 ml. of a 3 percent aqueous hydrogen peroxide solution and 0.5 grampf the potassium salt of Cl(CF CFCl) CF COOH, the system is boiled for 10 minutes. Frothing is controlled by the amount of surface active agent added or by the use of a cold water spray if necessary. The system is cooled and the oil is separated and washed.

Example 3 Wood pulp is fed to a forming machine to produce a sheet which is dewatered and treated with a quantity of hydrogen peroxide solution suflicient to give the brightness desired (0.21.0 percent of H based on dry weight of pulp). One gallon of the bleaching solution contains 0.5 pound of 27.5 percent hydrogen peroxide, 1.5 pounds of sodium silicate, of 42 B. gravity, and 1 gram of the potassium salt of Cl(CF CFCl) CF COOH.

The impregnated sheet is shredded and transferred to a retention tower for 30 minutes to an hour, depending on the extent of color improvement needed. The pulp is then discharged into a suitable apparatus for neutralization and dilution to produce a stock from which paper can be made.

Example 4 1500 grams of commercial sorbitan monostearate is stirred at a temperature of 75 C. and treated with 5 grams of sodium chlorite (50 percent aqueous solution) and 0.5 gram of a salt of CI(CF CFCI) CF COOH for 30 minutes. The mixture is concentrated under vacuum and filtered with dilute alcohol washing.

Example 5 A soft wood kraft pulp is treated with 8 percent hypochlorite bleach at 8 percent stock density at 25 C. for one hour and then diluted to 40 percent stock density with suflicient chlorine water to give 2.5 percent chlorine, based on the weight of dry pulp, and is allowed to stand for one hour at room temperature; it is then washed, antichlored with S0 water and rewashed.

-In a second stage, the pulp is subjected to a hot caustic treatment with 1.5 percent sodium hydroxide at 15 percent stock density for two hours at 78 C. and then washed.

As a final stage, the pretreated pulp is bleached with 1 percent chlorine dioxide, based upon the dry weight of the pulp, for one hour and a half at 70 C. and a pH 5.8 in the presence of 0.3 gram/gallon of the potassium salt of Cl(CF CFCl) CF COOH. This is followed by washing, antichloring and final washing.

Example 6 A piece of acetate rayon fabric weighing 100 grams is immersed in a solution containing 500 ml. of aqueous sodium chlorite (25 grams of available chlorine), 1 liter of pH 7 phosphate butler solution, 400 ml. of a dilute solution of formalin containing 5 grams of formaldehyde and 0.5 gram of the potassium salt of The mixture is heated for one hour at 50 C., then washed and dried.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

I claim:

1. An aqueous oxidizing bath containing between about 0.01 and about 10 grams per liter of a water soluble substance selected from the group consisting of alkali metal and ammonium salts of a compound having the formula 0 Z(o F r-C F01) 0 Fz( iOH in which Z is selected from the group consisting of chlorine and perhalomethyl radicals having a total atomic weight not in excess of 146.5, and n is an integer from 2 to 10.

2. An aqueous oxidizing bath containing between about 0.01 and about 10 grams per liter of a water soluble substance selected from the group consisting of alkali metal and ammonium salts of a compound having the formula in which n is an integer from 2 to 10.

3. An aqueous oxidizing bath containing between about 0.01 and about 10 grams per liter of a water soluble compound having the formula in which Z is selected from the group consisting of chlorine and perhalomethyl radicals having a total atomic Weight not in excess of 146.5, 11 is an integer from 2 to 10, x is an integer from 1 to 4, and M is an alkali metal.

4. An aqueous oxidizing bath containing between about 0.01 and about 10 grams per liter of a water-soluble compound containing 4 to 33 carbon atoms selected from the group consisting of alkali metal and ammonium salts of a perchlorofluorocarboxylic acid.

References Cited in the file of this patent UNITED STATES PATENTS 98,387 Jeanning Dec. 28, 1869 2,559,629 Berry July 10, 1951 2,559,752 Berry July 10, 1951 2,676,985 Husted Apr. 27, 1954 2,678,953 Conly May 18, 1954 2,723,999 Cowen Nov. 15, 1955 2,727,923 Husted Dec. 20, 1955 2,732,398 Brice et al. Jan. 24, 1956 2,766,215 Stoops et a1. Oct. 9, 1956 

4. AN AQUEOUS OXIDIZING BATH CONTAINING BETWEEN ABOUT 0.01 AND ABOUT 10 GRAMS PER LITER OF A WATER-SOLUBLE COMPOUND CONTAINING 4 TO 33 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL AND AMMONIUM SALTS OF A PERCHLOROFLUOROCARBOXYLIC ACID. 